The present invention relates to a method and an apparatus for coating substrates, according to which the substrate is held on a substrate holder in such a way that the substrate surface that is to be coated is exposed, and the substrate is rotated together with the substrate holder.
An apparatus of this type is known, for example, from EP-A 0 711 108. This apparatus includes an initial coating station, whereby a downwardly directed substrate surface that is to be coated is moved past a capillary gap that is supplied with lacquer to coat the substrate surface. The substrate is subsequently moved to a centrifuging station and is rotated or centrifuged within a protective ring that serves to convey away residual lacquer that is centrifuged from the substrate.
DE-A-195 45 573 discloses an apparatus for the uniform application of a lacquer layer to a substrate, according to which a substrate is placed upon a rotary plate with the side that is to be coated facing upwardly. During a centrifuging process, a hood that at least partially covers the substrate is moved from above over the substrate and is slightly spaced therefrom, or is positioned directly upon the substrate.
DE-A-92 18 974 also discloses an apparatus for applying a thin layer, for example of lacquer, upon a substrate by means of a centrifuging device. The apparatus includes a rotary plate upon which a substrate that is to be coated is disposed with the surface that is to be coated facing upwardly. A hood can be positioned from above upon the rotary plate in order to form a chamber for receiving a substrate. In this connection, the chamber formed between the hood and the rotary plate is connected to the surrounding atmosphere by means of apertures in the rotary plate. Furthermore, elastic cover strips are provided on the hood and are in contact with upwardly directed edges of the substrate to form a chamber between the cover and the substrate.
U.S. Pat. No. 5,042,421 discloses a rotary head arrangement for coating a semiconductor, and includes a rotary plate for supporting the wafer and a disk that surrounds the wafer and can be secured to the rotary plate.
DE-A40 24 642 furthermore shows a rotary plate for receiving a substrate, which is held on the rotary plate by means of a vacuum.
These apparatus have the problem that the uniformity of the layer thickness achieved by the centrifuging process is not always adequate.
It is therefore an object of the present invention to provide a method and apparatus of the aforementioned type for treating substrates according to which a homogeneous coating of the substrate surface that is to be treated is achieved.